[photo of slug 211] [photo of slug 281] [photo of slug 514] [photo of slug 516]

A slug is a locomotive that has no diesel engine and no control cab. Its electric traction motors receive their power from another locomotive (called the "mother"). CN's slugs are used in yards at low speed; in fact slugs cut out over a certain speed. At higher speeds, the mother may not be able to produce enough power for the slug.

CN slugs in the series 200-209 are called "yard booster units". They were built new and work with 7200-series mothers.

CN slugs in the series 211-281 are built from old GP9 locomotives which are cut down and have their diesel engines removed. They usually operate with 7200-series mothers.

CN slugs in the series 500-522 are called "hump booster units". They were built new, and usually work with GP38-2 mothers in the 7500-series. Slug 514 above is shown attached to GP38-2 7518 with whom it usually works in Edmonton.